TM 1-6625-724-13&P
0073 00
0073 00-3
Rotor Smoothing Configuration
Two basic AVA programs are used to smooth the main and tail rotor of the OH-58D. One is OH-58DM, which is used
on aircraft with a Mast Mounted Sight (MMS) and is the preferred method and the other is OH-58D, which should be
used as a last resort if the MMS is not installed. These programs are stored in the CADU under the Aircraft Type
option of the Main Menu. The proper configuration for smoothing the OH-58D rotor is with the MMS installed and with
no external stores. Working the rotor without the MMS is obsolete.
Factory Settings of Blades
All rotor blades are mass balanced, have their trim tabs set, and have the tip tracking weights set against a master
blade at the factory to insure interchangeability. These settings are stenciled on the root end of the blade. Since the
blade is set to a master, the actual weight of the blade and the stenciled tip weight values mean nothing relative to
tracking and balancing the rotor. The tab setting is the recommended “zero” setting or starting point for the tab when
tracking new rotors.
Rotor Smoothing Adjustments
Pitch Links:
The pitch links are used primarily to track the rotor at idle rpm and as a fine adjustment for the vertical 1/REV in
forward flight. Pitch link adjustments affect the balance of the rotor. The AVA specifies pitch link adjustments in the
number of flats to increase or decrease blade pitch. Lengthening the pitch link increases blade pitch and shortening
the pitch link decreases blade pitch. Figure 1 shows the direction to turn the barrel to increase or decrease blade
pitch. Remember the coarse rod end is on the bottom so that it is the indication on which way to adjust the link, not
the upper rod end. Maximum allowed upper rod end thread exposure is 14. Maximum allowed lower rod end thread
exposure is 9.
Figure 1. Pitch Link Adjustment
Balance Weights
Balance weights are added to the rotor yoke to mass balance the rotor. With the MMS installed, an out-of-balance of
the rotor is detected by a 1/REV at idle. At 100% rpm the MMS absorbs most of the out-of-balance forces. On the
OH-58D the proper use of balance weights is to reduce the 1/REV vibration at idle. AVA specifies hub balance
adjustments as the number of grams to be added to or removed from the orange or red balance locations (obviously,
the opposite adjustment can be made to the opposite blade). The maximum balance weight that can be installed per
location is approximately 680 grams, which includes a maximum of four (212-010-710-3) weights split evenly between
the upper and lower side of the yoke. (Note: The U. S. Army has bought some steel 710-3 weights which weigh only
½ of the Bell supplied tungsten weights so use a scale if in doubt.) Bolts up to NAS6204-50 can be used. Longer
weight packages could contact the grip in extreme conditions.
D ecreasing Pitch
(- Adjustment)
Increasing Pitch
(+Adjustm ent)
